Oil well treatment



April 29, 1958 J. c. ALLEN on. WELL TREATMENT Filed July 26, 1955 tr to 2 832 llti N a 4' l w I y 1 it Q la'tenteel Apr. 29, lfihd method of preventing and/or reducing water-coming as evidenced by the production of a relatively large amount 2 832 416 of water with respect to produced petroleum hydrocaron. water. TREATMENT Joseph C. Allen, hellaire, 'ieze, assignur to The Texas Company, New York, N. Y., a corporation of Delaware Application July 26, 1955, Serial No. 524,466

a Claims. cl. 166-42) conin which sometimes results during the production of petroleum hydrocarbons from a hydrocarbon-producing formation which overlays'a substantially water-saturated formation.

Watenconing is a term given to the mechanism underlying the entry of bottom Waters into producing Wells. Petroleum hydrocarbons re often produced from porous subsurface formations which overlay a substantially watersaturated porous formation. Under static conditions the water, being of greater densitythan the hydrocarbons, remains beneath and at the bottom of the hydrocarbonproducing formation. At high rates of production of petroleum hydrocarbons however, the upper boundary or surface of the substantially water-saturated formation rises due to the increased flow of petroleum hydrocarbons into the well bore which extends into the liquid petroleumproducing formation immediately adjacent and above the substantially water'saturated formation. The rise of water into the hydrocarbon-producing formation and into the well bore represents a dynamic eilect in which the upward directed pressure gradients associated with the flow of the hydrocarbons into the'producing well bore are able to balance the hydrostatic head of the resulting elevated water column.

Various methods have been suggested heretofore to eliminate or to reduce the water-caning phenomenon. These methods have included reducing the well penetration into the hydrocarbon-producing formation so that higher production rates are possible without at the same time experiencing a relatively increased production of water therewith. Another method which has been suggested is to bottom the producing well into a substantially water-impermeable formation. These indicated methods, however, cannot be successfully employed in all instances to eliminate or reduce water-coning. Certain undergound hydrocarb on-producing formations are only a relatively few feet in thickness. Accordingly, reducing the well here penetration into a formation would unduly restrict the recovery of petroleum hydrocarbons therefrom. Other hydrocarbon-producing formations do not have associated therewith an immediately underlying water-impermeable formation.

it is an object of this invention to provide an improved method for the recovery of petroleum hydrocarbons.

it is another object of this invention to provide an improved method for the recovery of petroleum hydrocarbons from a petroleum hydrocarbon-producing formation which overlays a substantially water-saturated formation.

it is still another object of this invention to provide a bons during the production of petroleum hydrocarbons from a well bore extending into a petroleum-producing formation in contact with and adjacent under-lying waterproducing formation.

it is still another object of this invention to provide an improved method of well completion and well production wherein the well bore extends into a liquid petroleumproducing formation which overlays a water-producing formation.

These and other objects of this invention and how they are accomplished will become apparent with reference to the accompanying drawing wherein:

Fig. 1 schematically illustrates the water-coning phenomenon; and

Fig. 2 schematically illustrates a method in accordance with this invention for overcoming water-caning.

in accordance with this invention water-coiling is overcome by injecting into the hydrocarbon-producing formation in the zone experiencing the water-coining phenomenon a substantial amount of a fluid. As the fluid is injected into that portion of the hydrocarbon-producing formation experiencing water-coning, the Water filling the pores or interstices of the formation is displaced and forced back by the injected fluid. The injection of fluid is continued until the water has been displaced a substantial radial distance, e. g., at least about 5 feet, preferably at least about 20 feet, from the point of fluid injection, which is conveniently the well bore itself. initially, the pores of this zone of the hydrocarbon-producing formation may be substantially saturated with water, i. e., 70-90 percent occupied by water, particularly if the well produces almost 106% water. It is preferred in the practice of this invention to reduce the water content of the pores of the formation to-the irreducible minimum for a substantial extent in the area surrounding the location of fluid injection. Depending upon the geometrical configuration of the pores or interstices of the formation the irreducible minimum water content is usually in the range 2-5=3 percent of the pore space.

Various fluids such as gases and hydrocarbon and petroleum liquids and similar non-aqueous liquids may be employed in the practice of this invention. Suitable gases include natural gas, usually associated with and dissolved in a liquid petroleum-producing formation and which is recovered by suitable means, such as a gasliquid separator at the surface. It is preferred that the injected natural gas be dry, that is, having had its natural gasoline content stripped therefrom and substantially free of water vapor. Another gas which may be employed in the practice of this invention is air. Still another gas which is suitable in the practice of this: invention is a gaseous mixture of combustion products such as a flue gas and the like, usually containing nitrogen, carbon dioxide, and other gases in varying amounts. it is possible in the practice of this invention to reduce the water content or saturation of the formation into which the fluid is injected, to an amount below the so-called irre ducible minimum obtainable by mere volumetric displacement, by injecting into the formation a hot gas, such as hot combustion gases, so as to substantially dry the formation into which this gas is injected. in accord ance with another aspect of this invention there is added to the injected gas a small amount of a vaporiaed material which deposits within the formation in the zone of gas injection a film preferentially wettable by oil, e. g, a hydrophobic film. Suitable materials include the halosilanes containing hydrocarbon groups such as the alkyl chlorosilanes includin monomethyl dichloro-utonosilane,

dimethyl dichloro-monosilane, diethyl dichloro-monosilane, dipropyl dichloro-monosilane, dibutyl dichloro monosilane, triethyl monochloro-moncsilane and the like, which readily hydrolize upon contact with water to form a hydrophobic film within the interstices of the formation. This hydrophobic, preferentially oil-wetted film further reduces the water-permeability of the formation wherein the gas is injected. Also suitable are the aryl and aralkyl halo-silanes.

Suitable hydrocarbon liquids which may be employed in the practice of this invention include crude oil substantially as produced from the well undergoing treatment, stock tank oil, normally liquid petroleum distillate fractions, such as a gas oil or lubricating oil fraction, preferably a viscous, high boiling liquid petroleum fraction, e. g. initial boiling point not less than 300 F, preferably not less than 400 F. The injection of a petroleum liquid is preferred in the practice of this invention since better displacement of the wateris thereby obtained and there is less likelihood of channeling of the injected liquid into the water hearing or producing formation taking place.

Referring now to Fig. l of the drawing which schematically illustrates the water-coning phenomenon, a subsurface gaseous and/or liquid petroleum hydrocarbonproducing formation is indicated at 11. An immediately underlying, substantially water saturated, water-producing formation is indicated at 12. A well bore 13 extends into the petroleum-producing formation 11 and is bottomed in the water-producing formation 12. A pro duction casing 14 is provided with perforations 15 within the petroleum-producing formation 11. Under static conditions or at a relatively low rate of petroleum production from the petroleum formation ill, the upper surface of the water-producing formation is located at about the position indicated by the dashed line 16. At relative- 1y high rates of production, and/or, because of the upward directed pressure gradients associated with the flow of petroleum into perforations 15, the water table rises to the extent it is balanced by these upward directed pressure gradients. As the water table rises, as indicated by solid line 17, into the zone of production of liquid petroleum hydrocarbons, water is produced by the lowermost perforations 15 of casing 14. At still greater rates of production from formation 11, the water table continues to rise and there results a greater production of water relative to the amount of produced petroleum. The above-described phenomenon is commonly known as water-coming.

Referring now to Fig. 2 of the drawing, there is schematically illustrated therein a method according to this invention for preventing and/or reducing watepconing. The same reference numerals have been employed in Fig. 2 as were employed in Fig. l for reasons of clarity and ease of understanding. As indicated in Fig. 2, well bore 13 provided with casing 14 extends into petroleum-producing formation 11 which overlays water-producing formation 12. In order to prevent and/or reduce waterconing when the production of petroleum is commenced or to purge the petroleum-producing formation of water which has invaded the petroleum-producing formation 11 because of water-coning, the casing 14 is perforated within the petroleum-producing formation 11 near the top or upper surface thereof and near the bottom and/ or in the upper part of the water-producing formation 12 as illustrated. Packing 18 is then inserted within casing 14 intermediate the upper and lower perforations 15. Dashed line 16 indicates the normal interface of formations 11 and 12. After the packing in has been installed; a fluid such as stock tank oil, a high boiling petroleum distillate fraction or dry natural gas is injected via conduit 19 into the formation 11 via the lower perforations 15 in the casing 14 and removed from formation it via upper perforations 15 for recycle back into conduit 19 back to the surface via the annular space between conduit 19 and casing 14. The injection of fluid into formation 11 is continued until the water has ben displaced within formation 11 for a substantial radial distance surrounding that portion of well bore 13 within formation 11, to the extent indicated by dashed line 21. After a sufiicient amount of fluid has been injected to displace the water from around the well bore 13 immediately adjacent the liquid petroleum producing formation 11, the injection of fluid is stopped and the production of petroleum from formation 11 is commenced. As the liquid petroleum flows through perforations 15 into production casing 14, upward-directed pressure gradients are created which tend to lift the water table into the petroleum formation 11 in the area of the well bore 13. Accordingly, the water present within the water-producformation 1.2 tends to fill the spaces or pores of formation 11 from which it was displaced by the injected fluid. However, the flow of water thereiuto is resisted because of the reduced permeability of this localized portion of formation 11 due to the presence of a substantial amount of injected fluid present in the interstitial voids thereof. Due to the reduced permeability of this Zone considerable resistance to the flow of water therethrough is experienced with the result that the rate of petroleum production through perforations 15 can be greatly increased without experiencing an undue amount of produced water due to water-coming.

The practice of this invention is applicable not only to newly-drilled wells but is also applicable to previously drilled wells which are producing a considerable amount of water due to the phenomenon of water-coming. In accordance with a preferred embodiment of this invention particularly applicable to previously drilled producing Wells which exhibit an unduly large amount of water production due to water-coming, the producing well is shut in for a period of time necessary to approach or establish equilibrium conditions in the subsurface producing formations. This period of time, depending upon various circumstances, may be three hours to a month. Thereafter a liquid petroleum fraction is injected into and cycled within the hydrocarbornproducing formation as described hereinabove. After a sufiicient amount of liquid petroleum has been injected and cycled to force the water in the petroleum-producing formation a substantial radial distance outwardly from the well bore the injection of liquid petroleum is continued and petroleum production commenced. This technique drastically changes the normal pressure gradients set up around the well bore and prevent premature invastion or coming of Water into the petroleum producing formation. Obviously the injection rate of the recycled petroleum liquid would have to be less than the petroleum (oil and/or gas) production rate, as measured at the well head, the volumes being expressed in reservoir volumes, so that there is a net production of petroleum from the formation.

The method of this invention is applicable not only to so-called gas-drive petroleum reservoirs but also to socalled water-drive reservoirs.

As will be apparent to those skilled in the art, many substitutions, alterations or omissions are possible without departing from the spirit or scope of this invention.

I claim:

1. A method of producing petroleum hydrocarbons and inhibiting water-coming during the production of petroleum hydrocarbons from a well bore which peneface formations in a zone surrounding said well bore,

injecting via said well bore a non-aqueous fluid into the lower portion of said hydrocarbon-producing formation to reduce the water content in that portion of the formation to at least the so-called irreducible minimum, depositing within said lower portion of said hydrocarbompro ducing formation a preferentially oil wettable, hydrophobic film to increase the oil permeability and reduce the water permeability of that portion of the formation thus treated, injecting via said Well bore a non-aqueous fluid into said lower portion of said hydrocarberr-producing formation, withdrawing via said well bore the injected fluid from the upper portion of the hydrocarbonproducing formation and continuously injecting and withdrawing said fluid while at the same time producing via said well bore petroleum hydrocarbons from the upper portion of said hydrocarbon-producing formation, the volume of fluid injected being less than the volume of Withdrawn fluid plus the volume of produced petroleum hydrocarbons, said volumes being expressed in reservoir or formation volumes.

2. A method in accordance with claim 1 wherein said fluid is a liquid petroleum fraction.

3. A method in accordance with claim 1 wherein said fluid is crude oil recovered from said hydrocarbon-producing formation.

4. A method of producing petroleum from a well bore which penetrates a subsurface petroleum-producing formation which is in contact with and overlays a waterproducing formation which comprises establishing substantially equilibrium conditions within said formations in a zone surrounding said Well bore, introducing into the lower portion of said petroleum-producing formation within said zone via said well bore hot combustion gases to reduce the water content of that portion of the forma tion thus treated to a value below the so-called irreducible minimum, depositing Within the thus-treated portion of the petroleum-producing formation a hydrophobic film to render that portion of the formation preferentially oil wettable, injecting via said well bore a liquid petroleum fraction having an initial boiling point of not less than about 300 F. into the lower portion of said petroleumproducing formation containing said preferentially oil wettable, hydrophobic film deposited therein, Withdrawing via said well bore the injected liquid petroleum frac tion from the upper portion of the petroleum-producing formation and continuously injecting and withdrawing said petroleum fraction while at the same time producing petroleum via said well here from the upper portion of said petroleum-producing formation, the volume of said liquid petroleum fraction injected into said formation being less than the volume of said withdrawn liquid petroleum fraction plus the volume of produced petroleum, said volumes being expressed in reservoir or formation volumes.

5. A method of producing petroleum hydrocarbons and inhibiting water coning during the production of petro leum hydrocarbons from a well bore which penetrates a subsurface petroleum-producing formation which is in contact with and overlays an adjacent water-producing formation which comprises establishing substantially equilibrium conditions within said subsurface formations in the zone surrrounding said well bore, reducing the water content within said zone to a value below the socalled irreducible minimum by introducing into said zone via said well bore hot combustion gases, depositing within said formation in said zone a hydrophobic film to render that portion of said formation within said z ne preferentially oil wettable, injecting via said well bore within said zone a gas into the lower portion of said petroleum-pro ducing formation, withdrawing via said well bore the injected gas from the upper portion of said petroleumproducing formation, and continuously injecting and Withdrawing said gas while at the same time producing via said well bore petroleum from the upper portion of said petroleum-producing formation, the Volume of gas injected being less than the volume of withdrawn gas plus the volume of produced petroleum, said volumes being eX- pressed in reservoir or formation volumes.

6. A method in accordance with claim 5 wherein said gas is natural gas.

7. A method in accordance with claim 5 wherein said gas is natural gas previously recovered from said petroleum-producing formation.

8. A method of producing petroleum hydrocarbons and inhibiting water coning during the production of petroleum hydrocarbons via a Well bore which penetrates a subsurface petroleum hydrocarbon-producing formation which is in contact with an adjacent formation from which coning originates which comprises establishing substantially equilibrium conditions within said formations in a zone surrounding said well bore, introducing hot combustion gases into said zone within said hydrocarbonproducing formation to reduce the water content therein to a value below the so-called irreducible minimum, treating said zone within said hydrocarbon-producing formation to render that portion of the formation within said zone preferentially oil wettable, injecting via said well bore a non-aqueous fluid into the thus-treated portion of said petroleum hydrocarbon-producing formation, withdrawing via said well bore the injected fluid from another portion of said hydrocarbon-producing formation and continuously injecting and withdrawing said fluid while at the same time producing via said well bore petroleum hydrocarbons from said hydrocarbon-producing formation, the volume of injected fluid being less than the volume of withdrawn fluid plus the volume of the produced petroleum hydrocarbons, said volumes being expressed in reservoir or formation volumes.

References Cited in the file of this patent UNITED STATES PATENTS 2,241,253 Garrison May 6, 1941 2,241,254 Garrison May 6, 1941 2,258,616 Kendrick Oct. 14, 1941 2,377,529 Stephenson June 5, 1945 2,412,765 Buddrus etal. Dec. 17, 1946 2,469,354 Bond May 10, 1949 2,582,148 Nelly Jan. 8, 1952 2,749,988 West June 2, 1956 

